Abrasive coated sheet



Patented Sept. 19, 1939 PATENT OFFICE ABRASIVE COATED SHEET Nicholas E. Oglesby, Troy, N. Y., assignor to Behr- Manning Corporation, Troy, N. Y., a corporation of Massachusetts No Drawing. Application July 6, 1936 Serial No. 89,269

6 Claims.

The invention relates to coated abrasives particularly of the type having a paper or matted or felted fibre base, and with regard to its more' specific features to such abrasives with water soluble adhesives, such as animal glues, casein,

. "sodium silicate and the like.

One object of the invention is to provide a more flexible paper backing for coated abrasives, to the ends that the sanding of curved surfaces such as table legs and. chair legs or other objects having flutes, designsor carvings may be efliciently and readily performed. Another object of the invention is to provide a paper particularly applicable for the sanding of corners, right angle unions, recesses and other surfaces havingsharp angles or convolutions. Another object of the invention is to provide an abrasivepaper comparatively immune to cracking, that is to say which can be bent and even folded without cracking the backing. Another object of the invention is to provide a paper backing which cooperates with the coating to prevent peeling. Another object of the invention is to provide a process for the manufacture of relatively flexible abrasive paper capable of embodiment in a great variety of paper weights and finished products. Another object of the invention is to produce a paper backing which may be coated with water soluble adhesives and abrasive grains without excessive penetration of the adhesive into the pores of the paper, such penetration having usually resulted in a brittle product and a product lacking uniformity of the coating of the adhesive, due to the greater penetration of the adhesive into the less dense spots of-the paper as compared with less penetration into the more dense lumps .of the paper formation. Another object of the invention is to accomplish one or more of the foregoing while at the same time retaining relatively longfibres in the paper backing, such long fibred paper being more flexible and having a greater tear strength than a corresponding paper made with very short or excessively beaten fibres. Another "object of the invention is to provide a coated abrasive paper of relatively high tear strength. Another object of the invention is to provide a simple and practical process for manufacture of paper having one or more of the characteristics indicated. Other objects will be in part obvious or in part pointed out hereinafter.

'The invention accordingly consists inthe features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and orderof each of said steps to one or more of the others thereof, all as light weight paper producing a more flexible will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

A's conducive to a clearer understanding of the present invention, I note that for satisfactory use in the manufactureof coated abrasives, the paper backing should be relatively non-absorbent when treated with the binding adhesive which is used to hold the grits; otherwise the adhesive sinks into the paper and produces the effect of a starved joint and relatively poor bonding of the grits as well as a brittle backing sheet. In the past it has been recognized that excessive penetration by the making coat of adhesive, as for instance animal glue, is undesirable since excessive penetration sometimes produces a starved joint and poor bonding of the grit as well as a very brittle short tearing backing. It has therefore been customary to beat the paper pulp to a relatively advanced degree of hydration so as to -form a dense sheet. This procedure has neces fore coating and a shorter fibred relatively tinny backing which is more resistant to penetration by the water soluble adhesives used in making coated abrasives.

An important class of coated abrasives where flexibility is required is known to the trade as finishing papers and will be used in this specification by way of illustration. The so-called finishing papers are usually made on 40 lb. paper, a

40 product than similar heavier papers. Paper stock used for finishing paper has usually been prepared from rope, jute, kraft or a mixture of these fibres.

By way of illustration of my invention, a suit- 45 able furnish may consist of per cent rope fibre suitably cooked as is known in the'art and 40 per cent of a good grade of kraft pulp. The furnish is introduced into a paper beater and the paper, stock is beaten to the required degree, the exact degree of beating depending upon the subsequent treatment and use of the paper. In many cases I find'that the foregoing furnish should be beaten to a Schopper-Riegler test of 30 degrees. Less beating will'give a more absorbent sheet with longer fibres and more beating will give a less absorbent sheet with shorter fibres. After the paper pulp has been sufliciently beaten, it is run through a Jordan to a Fourdrinier paper making machine and the sheet is formed in the usual way. The paper may also be dried in the regular way and taken down in the form of large rolls. it may then be treated on tub sizing equipment or other suitable papertreating equipment in a variety of ways to produce a flexible, relatively non-porous product with longer fibres than would otherwise be possible if excessive penetration of the water soluble sandpaper binder is to be avoided.

A satisfactory paper treatment for one form of my invention may be made by dissolving 51 lbs. of

triethanolamine oleate in 175 lbs. of water. The

solution may be applied to the paper warm on tub sizing or similar equipment and the paper may then be dried and calendered in the usual way. The triethanolamine oleate-treated paper preferably contains about 30 to 40 per cent of the soap. In some cases animal glues may be added to the foregoing solution and byway of illustra-, tion we may add to the said solution about lbs. of an 86 millipoise animal glue. In this case the treatingsolution should be applied warm, for example 140 F. After the paper has been treated and dried the glue may be tanned with formaldehyde.

In lieu of triethanolamine oleate I may use triethanolamine linoleate or triethanolamine palmitate, adjusting the solution and the paper so that 30 to 40 per cent of the soap is incorporated in the sheet.

As'another treatment for the paper I may use a solution consisting of 80 lbs. of water, lbs. of 62 millipoise animal glue and 30 lbs. of glyc erine. In this case the solution should be applied to the paper in the tub sizing or similar operation at a temperature of about 140 F. and the paper should be dried over the usual paper drying cans.

' as, for instance, I may use a solution consisting being objectionable in the subsequent use of the coated abrasive product.

As an alternate treatment I may use sorbitol in liquid form of the type as made and sold. by the Atlas Powder Company. In this case, in the tub sizing operation after the paper is formed, a solution consisting of 80 lbs.- of water and 20 lbs. of sorbitol may be applied preferably at about 125 F. to 140 F. and the paper dried and calendered in the usual way. Paper prepared for this treatment is preferably formed after beating to a Schopper-Riegler test of about 50 degrees. The treated paper should contain 10 to 20 per cent sorbitol. U

I may also add glue along with the sorbitol of 80 lbs. of water, 5 lbs of 62 millipoise animal glue and lbs. of sorbitol. In this case the solution should be applied to the paper at a temperature of about 140 F. After the tub sizing operation, the paper is dried and the glue is tanned with a water solution containing 10 per cent formaldehyde as previously explained. In this case the base paper may be formed after the pulp is beaten to a Schopper-Riegler test of about 40 degrees.

It should be understood that in the treatment of my paper backing, I may firs-t form the paper on the paper making machine, remove it from the machine and apply the tub sizing or similar operations described, or I may add treatments after the paper has been formed and has been only partly dried or dried during its passage through the drying cans, by the customary arrangements for tub sizing on a paper making machine at a break in the drying can line.

Instead of a mixture of rope fibre and kraft, I may use an all-rope furnish or an all-kraft furnish or I may use paper made from jute or mixtures of jute with rope and kraft as well as some cotton-and other fibres such as purified wood fibres..

The paper treatments cited are by way of illustration. Many variations may be made in the solutions given by way of illustration and other materials may be used. The foregoing procedure involves plasticizing or softening the paper and for this purpose I employ materials which have a definite softening action on cellulosic fabrics, such materials being for example triethanolamine oleate, glycerine or sorbitol, and others as previously mentioned. 'Triethylene glycol is also a softener for cellulosic fabrics and may be used to replace glycerine. Diethylene glycol, while it has a softening effect on cellulosic fabrics is relatively more volatile than the compounds used by way of illustration and is not therefore preferred. Of the materials cited sorbitol and triethanolamine oleate are relatively nonvolatile and more permanent and are therefore preferred treatments.

These plasticizers or softeners for cellulose have a definite softening or flexifying effect on the paper, irrespective of the fibre length or degree of beating and may be used even though the paper stock has been beaten so as to form a relatively non-porous sheet. However, these agents also serve to swell the fibres and decrease the porosity of the paper so that a backing which would otherwise be too porous or absorbent can be readily coated.

Another aspect of my invention comprises, in addition, thefilli'ng of the pores of relatively long fibred paper with a plasticized adhesive, so that it will be coatable without excessive penetration of the grit binding adhesive material into the paper backing with the aforementioned disadvan. tages ofsuch penetration. I sometimes mix with cellulose softening agents, a material such as animal glue, the plasticizers given by way of illustration as being combined with glue, serving to plasticize the animal glue as well as cellulosic fabrics. As a general proposition the adhesive used in the paper treating solution should have combined therewith a material or a mixture of materials which serves to plasticize both the cellulosic backing and the adhesive. So far as I am aware, materials which serve to plasticize or soften both cellulosic fabrics and water soluble adhesives are themselves water soluble. I

Forty pound paper made and treated by the processes given b Way of illustration is a satisfactory backing for coated abrasives made with water soluble adhesives and is of particular value in making the so-called finishing papers which may be coated with various abrasive materials such as garnet, fused alumina, silicon carbide and, the like. Finishing papers are usually made m, grit sizes' from 10/0-400 to 0-80 inclusive. By

way of illustration I will describe in detail the manufacture of 4/0 fused alumina finishing paper. Thebacking prepared as heretofore described is mounted and used by customary processes on a sandpaper making machine. As a making coat I then apply to the paper backing, a coating of 33 per cent of 86 millipoise hide glue. A suitable temperature for applying the glue solution to the backing is about 145 to 160 F. The coating of grits .is then applied by the usual means and in this case we will consider by way of illustration anopen coating. A suitable sand weight in this case is about 4.8 lbs. per sandpaper ream. The grits are applied by a suitable open coating device at a controlled rate, the adhesively coated web also being run at a controlled and constant speed. After this abrasive coating is applied to the adhesively coated web, the web is allowed partially to dry or dry in festoon form and is then run through a sandpaper sizing machine where a sizing coat of adhesive is applied over the adhesively retained abrasive grains. For the sizing operation a 22 per cent solution of 86 millipoise hide glue will be found satisfactory. This sizing coat may be applied conveniently at a temperature of about 145 to about 160 F. The sand sizedweb is then conveyed to a conventional sandpaper drying room, festooned, dried and taken down in the form of rolls. The rolls may then be cut into suitable form for final use such as 9" x 11" sheets or other convenient forms and shapes.

Instead of an open coating a close coating may be applied if desired. While finishing papers have been used by way of illustration, so-called ream papers may be made in the same manner, and in this case it is customary to use or lb. base weight paper instead of 40 lb. paper and coarse as well as fine grits are coated, for example 2'36 to 9/0-320. The process may also be used for abrasive goods coated on an E weight or 1b. backing or for any grit size on any backing that is required where flexibility and lack of penetration of the making coat of ad- 45 hesive into the paper backing is advantageous.

The process is applicable not only to sheet goods, commonly known as ream goods, but may also be used for roll goods, discs, or other forms of coated abrasives.

Animal glue, for example hide glue, is a preferred water soluble adhesive for coating and sizing the abrasive grits, but I may also use casein, sodium silicate and other suitable water soluble adhesives.

It will thus be seen that there has been provided by this invention a method and an article in which the various objects hereinbefore set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described may be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. Abrasive coated paper comprising a paper backing sheet containing as a softening agent triethanolamine oleate, and abrasive grits attached to said backing by means of a water soluble adhesive.

2. Abrasive coated long fibered paper comprising a paper backing sheet containing as a softening agent sorbitol, and abrasive grits attached to said backing by means of a water soluble adhesive.

3. Abrasive coated paper comprising a paper backing sheet containing as a softening agent triethanolamine oleate and abrasive grits attached to said 'backing by means of an animal glue.

4. Abrasive coated long flbered paper comprising a paper backing sheet containing as a softening agent sorbitol, and abrasive grits attached to said backing by means of an animal glue.

5. Abrasive coated paper comprising a paper backing sheet permeated with animal glue and triethanolamine oleate, and abrasive grits 'attached to said backing by means of a water soluble adhesive.

fihAbrasive coated paper comprising a paper backing sheet permeated with animal glue and sorbitol, and abrasive grits attached to said backing by means of a water soluble adhesive.

NICHOLAS E. OGLESBY. 

